It would easily be possible, because all custom wands are essentially still wands, just with a different sprite and custom stats. It's up to the mod authors to make them usable on the anvil, all that is needed is the "wand" tag. But most mod authors don't wand them to be usable on the anvil because you would either very easily get an extremely overpowered wand, or a really bad one since all it does is average the stats of both input wands.

Hm ok thanks that makes sense. One of my favorite things to do is wand, double tablet over and over on the same wand, fun stuff thanks for the reply.